In LTE-A, in order to improve the cell average spectrum utilization efficiency and the cell edge spectrum utilization efficiency, Coordinated Multi Point Transmission/Reception (CoMP) technology is employed. CoMP technology is classified into DL CoMP (downlink CoMP) and UL CoMP (uplink CoMP), both of which can improve the average spectrum efficiency of a cell and the quality of service of a cell edge user to a great extent. CoMP is divided into the following four scenarios:
scenario 1: a homogeneous network with intra-site CoMP;
scenario 2: a homogeneous network with high transmit power (Tx) RRHs (Remote radio head);
scenario 3: a heterogeneous network with low power RRHs within the macro cell coverage, wherein the RRHs and the macro cell have different cell IDs;
scenario 4: a heterogeneous network with low power RRHs within the macro cell coverage, wherein the RRHs and the macro cell have the same virtual cell IDs.
In LTE R8/R9/R10 protocol versions, the formats of the PUCCH channel can be divided into three categories, seven types of formats totally. The first type contains three formats, i.e., format1, format1a and format1b, the second type also contains three formats, i.e., format2, format2a and format2b, and the third type contains one format, i.e., format3. The first type of PUCCH is used for transmitting scheduling request (SR) and acknowledgement (ACK)/negative acknowledgement (NACK) signalling. The second type of PUCCH is mainly used for transmitting channel state information (CSI). Currently, the third type of PUCCH is mainly used for feeding back the ACK/NACK signalling of a plurality of cells in the case that the UE is configured with a plurality of serving cells under the carrier aggregation scenario. As shown in FIG. 1, it is a schematic diagram showing the resource allocation of a PUCCH on one slot. In FIG. 1, the mixed resource block (RB) represents that both the format1/1a/1b and the format2/2a/2b exist in this RB at the same time, and there is at most one mixed RB in one slot; the parameter N(2)RB represents the number of physical resource blocks (PRBs) occupied by format2/2a/2b, and this parameter is configured by the upper layer.
For the first type of PUCCHs, the available resource n_r is represented by three sub-resources, which are respectively: (n_cs, n_oc, n_PRB), wherein n_cs represents the resource sequence number of cyclic shift (CS), n_oc represents the resource sequence number of orthogonal code (OC), and n_PRB represents the resource sequence number of PRB. These three sub-resources are in a one-to-one correspondence with the resource index n(1,p)PUCCH. For the second type of PUCCHs, the available resource n_r is represented by two sub-resources, which are respectively: (n_cs, n_PRB). The available resources of the second type of PUCCHs are in a one-to-one correspondence with the resource index n(2,p)PUCCH. For the third type of PUCCHs, the available resource n_r is represented by two sub-resources, which are respectively: (n_oc, n_PRB). The available resources of the third type of PUCCHs are in a one-to-one correspondence with the resource index n(3,p)PUCCH.
The resource index n(1)PUCCH of format 1 in the first type of PUCCHs is configured by the upper layer. The value of the resource index n(1)PUCCH of PUCCH format 1a/1b on subframe n can be obtained by two methods, which will be described as follows by taking the case where the UE is configured with one serving cell in a frequency division duplex (FDD) system as an example.
If the physical downlink shared channel (PDSCH) on subframe n-4 of the main serving cell does not detect the corresponding physical downlink control channel (PDCCH), then the above-mentioned n(1,p)PUCCH will be obtained according to upper-layer configuration and Table 1, and such kind of ACK/NACK is referred to as semi-static ACK/NACK (which can also be referred to as semi-static A/N) herein.
If the PDSCH on subframe n-4 of the main serving cell detects a corresponding PDCCH, or this PDCCH is used for indicating downlink semi-static scheduling (SPS) release, then the above-mentioned n(1,p)PUCCH will be obtained according to the following manner n(1,p=p0)PUCCH=nCCE+N(1)PUCCH, where nCCE represents the index of the first control channel element (CCE) of the PDCCH, N(1)PUCCH is a parameter configured by the upper layer and represents the number of resource indexes reserved for SRs and semi-static ACK/NACK (which can also be referred to as SR as well as semi-static A/N). FIG. 2 is a schematic diagram showing the resource index configuration of a PUCCH. For the channel resources of the second antenna port, n(1,p)PUCCH will be obtained in the following manner: n(1,p=p1)PUCCH=nCCE+1+N(1)PUCCH, and such kind of ACK/NACK is referred to as dynamic ACK/NACK (which can also be referred to as dynamic A/N).
TABLE 1TPC domainnPUCCH(1, p)‘00’The first PUCCH resource valueconfigured by the upper layer‘01’The second PUCCH resource valueconfigured by the upper layer‘10’The third PUCCH resource valueconfigured by the upper layer‘11’The fourth PUCCH resource valueconfigured by the upper layer
In this table, the transmission power control (TPC) domain is on a corresponding PDCCH.
n(2,p)PUCCH is configured by the upper layer. The resource index n(3,p)PUCCH of the third type of PUCCHs is obtained according to upper-layer configuration and Table 2.
TABLE 2TPC domainnPUCCH(3, p)‘00’The first PUCCH resource valueconfigured by the upper layer‘01’The second PUCCH resource valueconfigured by the upper layer‘10’The third PUCCH resource valueconfigured by the upper layer‘11’The fourth PUCCH resource valueconfigured by the upper layer
Then, after the available resource is obtained according to the resource index and the parameter configured by the upper layer, a channelization process will be performed, wherein the channelization processes of different formats of PUCCHs are different, which will be described simply hereinafter respectively.
The channelization process of format1/1a/1b is as follows: a data bit is modulated, then multiplied with CS and expanded to 12 subcarriers, then multiplied with OC code to realize time domain expansion, and then is subjected to code channel scrambling, and the obtained symbol will be mapped to a corresponding PRB.
The channelization process of format2/2a/2b is as follows: a data bit is scrambled first, then modulated, then multiplied with CS, and the obtained symbol will be mapped to a corresponding PRB.
The channelization process of format 3 is as follows: a data bit is scrambled first, then modulated, then multiplied with OC code and phase rotated, then cyclic shifted at a cell-specific symbol level, and discrete Fourier transformed (DFT) and then mapped to a corresponding PRB.
In LTE R8/R9/R10 protocol versions, a user equipment (UE) corresponds to one PUCCH channel. For a PUCCH channel, different UEs in a cell are multiplexed in a code division multiplexing (CDM) or frequency division multiplexing (FDM) manner, wherein the UEs are allocated to different PRBs in the FDM manner, and the UEs adopt different cyclic shift sequences (CSs) or different orthogonal codes (OCs) in the CDM manner. Here, different cyclic shift sequences refer to different cyclic shifts corresponding to the same root sequence. The root sequence is a computer-generated constant amplitude zero auto-correlation (CG-CAZAC) sequence with a length of 12, different cyclic shifts of the same root sequence are orthogonal to each other, and different root sequences are not orthogonal to each other. The root sequence is in a one-to-one correspondence with the cell ID. Therefore, the PUCCHs within the same cell are orthogonal to each other, and the PUCCHs from different cells with different cell IDs are not orthogonal to each other.
In LTE R10 protocol version, in order to reduce inter-cell interference, inter-cell interference randomization is performed for all PUCCH formats by using cyclic shift at a cell-specific symbol level.
Therefore, in LTE R8/R9/R10 protocol versions, when cell IDs are different, the PUCCHs among cells are not orthogonal. In CoMP scenario 3, the cell IDs of the macro cell and the RRH are different, while the UE of the macro cell and the UE of the RRH may send the PUCCH over the same time frequency resource, and in this case, the PUCCHs of the two UEs are not orthogonal. When the UE of the macro cell is at the edge of the RRH coverage and the power of the sent PUCCH is relatively large, if the power of this PUCCH reaching the RRH is comparable to the PUCCH power sent by the RRH UE or greater than the PUCCH power of the RRH UE, the PUCCH sent by the RRH UE will be interfered seriously, which renders the quality of the PUCCH signal received by the RRH to be very poor. In the case of joint reception of uplink (UL) CoMP, a plurality of nodes jointly receive the PUCCH sent by the same UE, if the target PUCCH comes from a neighbour cell, the PUCCH from the current cell will interfere with the target PUCCH since this target PUCCH is not orthogonal to the PUCCH in the current cell, which renders the receiving quality of the target PUCCH to be very poor and seriously affects the CoMP gain.
Aiming at the problem of great interference between PUCCHs from different cells in the related art, no effective solution has been presented currently.